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Recently, photoelectrochemical conversion (PEC) of water into fuel is attracting great attention of researchers due to its outstanding benefits. Herein, a systematic study on PEC of water using CuFe2O4/ α-Fe2O3 composite thin films is presented. CuFe2O4/ α-Fe2O3 composite thin films were deposited on two different substrates; (1) planner FTO glass and (2) 3-dimensional nanospike (NSP). The films on both substrates were characterized and tested as anode material for photoelectrochemical water splitting reaction. During PEC studies, it was observed that the ratio between two components of composite is crucial and highest PEC activity results were achieved by 1:1 component ratio (CF-1) of CuFe2O4 and α-Fe2O3. The CF-1 ratio sample deposited on planar FTO substrate provided a photocurrent density of 1.22 mA/cm2 at 1.23 VRHE which is 1.9 times higher than bare α-Fe2O3 sample. A significant PEC activity outperformance was observed when CF-1 ratio composite thin films were deposited on 3D NSP. The highest photocurrent density of 2.26 mA/cm2 at 1.23 VRHE was achieved for 3D NSP sample which is around 3.6 times higher than photocurrent density generated by α-Fe2O3 thin film only. The higher photocurrent densities of 3D nanostructured devices compared to planar one are attributed to the enhanced light trapping and increased surface area for photoelectrochemical water oxidation on the surface. The difference between valence and conduction bands of CuFe2O4 and α-Fe2O3 allows better separation of photogenerated electrons and holes at the CuFe2O4/ α-Fe2O3 interface which makes it more active for photoelectrochemical water splitting. © 2016 American Chemical Society.

Co ions with 100 keV energy with a fluence of 1 x 10(15) cm(-2) are implanted into ZnO(0001) single crystals at 300 degrees C under vacuum. The resulting Co-implanted ZnO single crystals and the subsequent 750 degrees C and 900 degrees C annealed samples are analysed with respect to their structural, optical, electronic, magnetic and ac electrical properties. Photoluminescence and X-ray photoelectron spectroscopy results indicate the signatures of the Co2+ state and its substitution at the tetrahedrally coordinated Zn-sites. X-ray diffraction and X-ray photoelectron spectroscopy identify the presence of the ZnCo2O4 and Co3O4 phases in the 900 degrees C annealed sample. By comparing the resistance response of the identified phases towards different magnetic environments, the impedance spectroscopy results successfully identify two magnetic phases (ZnCo2O4 and Co3O4) and a paramagnetic (Co-Zn) phase for the 750 degrees C and 900 degrees C annealed samples, implying the extrinsic nature of room temperature ferromagnetism. The observed ferromagnetism in each sample is not of single origin, instead the mutual effects of the secondary phases embedded in the paramagnetic host matrix are in competition with each other.

Co ions with 100 keV energy with a fluence of 1 x 10(15) cm(-2) are implanted into ZnO(0001) single crystals at 300 degrees C under vacuum. The resulting Co-implanted ZnO single crystals and the subsequent 750 degrees C and 900 degrees C annealed samples are analysed with respect to their structural, optical, electronic, magnetic and ac electrical properties. Photoluminescence and X-ray photoelectron spectroscopy results indicate the signatures of the Co2+ state and its substitution at the tetrahedrally coordinated Zn-sites. X-ray diffraction and X-ray photoelectron spectroscopy identify the presence of the ZnCo2O4 and Co3O4 phases in the 900 degrees C annealed sample. By comparing the resistance response of the identified phases towards different magnetic environments, the impedance spectroscopy results successfully identify two magnetic phases (ZnCo2O4 and Co3O4) and a paramagnetic (Co-Zn) phase for the 750 degrees C and 900 degrees C annealed samples, implying the extrinsic nature of room temperature ferromagnetism. The observed ferromagnetism in each sample is not of single origin, instead the mutual effects of the secondary phases embedded in the paramagnetic host matrix are in competition with each other.

Co ions with 100 keV energy with a fluence of 1 x 10(15) cm(-2) are implanted into ZnO(0001) single crystals at 300 degrees C under vacuum. The resulting Co-implanted ZnO single crystals and the subsequent 750 degrees C and 900 degrees C annealed samples are analysed with respect to their structural, optical, electronic, magnetic and ac electrical properties. Photoluminescence and X-ray photoelectron spectroscopy results indicate the signatures of the Co2+ state and its substitution at the tetrahedrally coordinated Zn-sites. X-ray diffraction and X-ray photoelectron spectroscopy identify the presence of the ZnCo2O4 and Co3O4 phases in the 900 degrees C annealed sample. By comparing the resistance response of the identified phases towards different magnetic environments, the impedance spectroscopy results successfully identify two magnetic phases (ZnCo2O4 and Co3O4) and a paramagnetic (Co-Zn) phase for the 750 degrees C and 900 degrees C annealed samples, implying the extrinsic nature of room temperature ferromagnetism. The observed ferromagnetism in each sample is not of single origin, instead the mutual effects of the secondary phases embedded in the paramagnetic host matrix are in competition with each other.

A range of metal-organic framework (MOF) materials, consisting of extended structures of coordination polymers incorporating paramagnetic metal ions (MnII,III,FeII, CoII,III, NiII and CuII) ,have been synthesized using bridging ligands such as carboxylate-decorated and/or nitrogen containing aromatics. The in situ. ligandtransformation of 1,2,3-benzene tricarboxylic acid into isophthalate to form four isomorphous coordination polymers was found to be highly dependent upon thereaction temperature, only occuring at higher temperatures such as 220°C. The structural and magnetic properties of all of the compounds have been studied indetail, with many showing bulk magnetic ordering and magnetic phase transitions. In [Co(bIM)(acetate)]n, benzimidazole complexation led to antiferromagneticsuperexchange interactions between the cobalt(II) ions, however at very low temperatures the magnetic behaviour changed from antiferromagnetic to weakferromagnetic ordering as a result of spin canting. Similarly, another 3D MOF [NiII2(pda)(OH)2(H2O)]n based on linear 1D NiII chains connected via Ni4O4-cubanes, has been synthesized, offering a rare example of a magnetic material in which the magnetic phase transitions (MPTs) are potentially coupled to slowrelaxation phenomena. This particular material showed an antiferromagnetic ordering at 21 K, with a magnetic phase transition from AF to CAF at 2.8 K. Wewere also able to design a topology in which the bulk magnetic ordering to higher temperatures were found to be shifted to considerably higher temperatures. Forexample, two 3D isostructural MOFs based on μ3-O centered metal clusters {[MIII3(pydc)3(μ3-O)]n.Cl, M = Mn, Co}, have been synthesized, displaying bulkmagnetic ordering at around 45 K; whilst only the cobalt based MOF displayed any spin canting behavior, and then only below 10 K. Other aspects of this thesisinvolved the introduction of flexible ligand systems such as 1,4-phenylene diacetic acid (pda) and di-(4-pyridyl)-et